It is known to provide a motor vehicle with a central door-lock system so that all of the doors, including the trunk and hood doors, can be locked and unlocked from a central location. Normally such a lock system is controlled from the latch for the driver's door so that by locking his or her door from the inside or outside the driver automatically locks all of the other doors of the vehicle. This system is particularly convenient in a large car where it would be fairly difficult for the driver to reach back and lock or unlock the back doors.
Normally a vehicle has door latches which each include a detent movable between a lock position securing the respective door to the respective doorpost and unlock position permitting separation of the respective door from the respective doorpost. Mechanism is provided for displacing this detent between the lock and unlock position. This mechanism includes inside and outside door handles, and an inside door button or lever and an outside door-lock cylinder. Usually the door handles are uncoupled by the mechanism from the detent when either the inside or outside door lock is operated. Nonetheless even if the door is locked from the outside it is normally possible to unlock it by raising the door button or lever on the inside. Thus it is also possible, even if the doors are locked, for a door to be opened by forcing the window to gain access to the inner door lock. It is further possible to slip a thin bar--a so-called "slim jim"--down into the door between the window and the outer door panel to operate the door mechanism and open up the door.
Typically in a central door-lock system each of the door latches is provided with a servoactuator basically formed as a reversible servomotor connected through appropriate link means to the respective door mechanism. This servoactuator is, therefore, connected in parallel normally to the inside door lock so that it can lock and unlock the door. All of these servomotors are in turn connected to a central switch that is normally incorporated with the inside and outside door locks of the driver's door. Thus when the driver locks or unlocks his or her door the other doors of the vehicle are automatically locked or unlocked. In this manner the driver is spared the effort of walking around the car to unlock or lock the passenger doors.
Such central lock systems, even though they are a considerable convience for the users, nonetheless in no way increase the security of the vehicle incorporating them. It is still just as possible for forced entry to be made of the vehicle in the manner described above.